How to tell when a view has become active

I'm using a navigationController to push a new view onto the stack. Once I'm done开发者_C百科 with that view I pop it. I want the original or root view at the bottom of the stack which then becomes active to know when this has happened to it can call a method on itself

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There are two options

1. implement -(void) viewWillAppear:animated: This is often a useful strategy for knowing that a view is about to become visible. If you are always doing the same thing when this happens, then this is quick and easy.

2. Send a NSNotification. This is useful when you want your underlying view to perform some action in response to a particular event happening elsewhere.

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Use the viewWillAppear delegate. It is called right before showing the view.